Viscosity compensator for fluid-pressure governors



June 19, 1928.

H. F. SCHMIDT VISCOSITY COMPENSATOR FOR FLUID PRESSURE GOVERNORS Filed Obt; 2, 1925 INVENTOR WITNESSE ATTORN EY Patented June 19, 1928 UNITED STATES PATENT OFFICE.

HENRY I. SCHMIDT, F LANSDOWNE, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPQRATION OF PENNSYLVANIA.

VISCOSITY COMPENSATOR FOR FLUID-PRESSURE GOVERNORS,

Application filed. October 2, 1925. Serial No. 60,130.

- My invention relates to fluid pressure operated governing apparatus wherein the fluid employed as the pressure medium is one having a varying viscosity due to its character or temperature such, for example, as lubricating oil, and has for its object the rovision of apparatus of the character deslgnated wherein the varying viscosity of the pressure medium is compensated for and variations in pressure due to variations in viscosity are eliminated.

Apparatus embodying features of my invention is illustrated in the accompanying drawing forming a part of this specification in which Fig. 1 is a sectional elevation of a turbine having my improved governing apparatus applied thereto; and Fig. 2 is a de- .tailed sectional view illustrating features of my invention.

In the operation of fluid pressure actuated governing apparatus employing oil or" other varying viscosity fluid as the pressure medium, difficulties have beenencountered due to the fact that the pressure developed by a pump varies to some extent with the viscosity of the oil. This is especially true of pumps which are characterized by positive displacement or by delivering a constant volume of fluid per revolution such, for example, as gear pumps. It is well known that a gear pump of itself develops no pressure but delivers a constant volume of fluid per revolution so that the volume of fluid delivered varies as the speed at which it is driven. By imposing a back pressure, such as by an orifice discharge, upon the fluid delivered from the pump, a pressure varying with the speed of the pump is developed. It the fluid employed as the pressure medium 40 be one of widely varying viscosity with changes in temperature, the pressure for a given speed of the pump discharging through an orifice of constant area becomes higher as the viscosity of the fluid increases and lower -as the viscosity of the fluid decreases.

Where oil is employed as the pressure'medium, the viscosity of the fluid may be doubled or tripled Within a range of of temperature. It will be obvious, therefore, 50 that where a area is employed for imposing a back pressure upon the fluid and the temperature of discharge orifice of constant the fluid varies through a considerable ran e, there may be wide variations in pressure or a given speed of the pump. I

In accordance with my invention, I employ a gear pump for developing fluld pres: sure for operating the governor and provide a dischar e orifice for the ump which imposes a bac pressure upon tihe fluid de- 00 livered therefrom. In addition to the discharge orifice, I provide valve controlled means which are adapted to increase the passage area through which the pump discharges. In order to operate the valve means in response to the viscosity of the pressure medium, I employ a second pump 7 driven in synchronism with the first pump and delivering fluid through relatively large passages against a low constant head into a vessel. The vessel is provided with an orifice of constant area below its upper level where by the fluid may flow therefrom and back into the reservoir by force of gravity. Inasmuch as the rate of flow from the vessel 7 is governed by the viscosity of the fluid and the height of fluid in the vessel above the orifice, the amount offluid in said vessel at all times is a measure ofthe viscosity of the fluid passing therethrough. The vessel is 30 connected through a suitable lever and linkages to the before mentioned valvemeans so that the valve means are operated re-- sponsive to the weight of fluid in the vessel.

Inasmuch as the governing of a prime mover is designed to be within comparatively narrow limits, the volume of fluid delivered by the last mentioned pump is substantially constant and is unaflfected by viscosity.

Referring now to the drawing for a better no understanding of my invention, I show in Fig. 1 at 10 an elastic fluid turbine having a motive fluid supply pipe 11 and an admission valve 12, the latter being controlled by a fluid pressure operated governing apparatus at 13. The governing apparatus at 13 may be of any approved design and is shown as 7 comprising a cylinder 7, a piston 8 connected to the valve 12 and operating in the cylinder 7, and a spring 9. At 1 is shown the turbine shaft which is adapted to drive, through worm gear teeth provided thereon, a pinion 16 and shaft 17. Connected to the lower end of the shaft 17 are two gear pumps 13 and 19 located within a fluid reservoir 2]. The gear pumps 18 and 19 are provided with a common fluid inlet 22. The ump 18 discharges fluid through a conduit 23 which is arranged to provide relatively large discharge passages for the pump and a low constant head therefor. The pump 19 delivers fluid through a conduit 24 to the governing apparatus 13. Connected to the conduit 2-1 is a branch conduit 26 terminating in an orilicc of constant area 27 through which fluid discharges continuously from the pump 19. lhe orifice 27 is of such area as to impose a back pressure upon the fluid within the conduit 24, said back pressure varying with the speed at which the pump 19 is driven.

At 28 I show a valve, which is preferably of the balanced type, and which is connected to the conduit 2!: through a passage 29. The valve 28 is adapted to permit a flow of fluid from the passage 29 back to the reservoir 21 through a passage 31 which is opened upon upward movement of the valve. In order that the valve 28 may be operated in accordance with the varying viscosity of the fluid, I provide a vessel 32 for receiving fluid discharged from the conduit 23. The vessel 32 is provided at its lower end with a drain tube providing an orifice of constant area which may be somewhat smaller in diameter than the discharge area of the conduit 23. Oil flowing from the conduit 23 flows into the vessel 32 and out through the oriiicc 33 back into the reservoir 21, maintaining a level in the vessel 32 in accordance with its viscosity.

As is well understood, the resistance of a fluid to flow through an opening or passage increases with its viscosity, and consequently a greater force is required to force it through it a constant flow is to be maintained. I pass all of the oil discharged from conduit 23 through vessel and consequently it must pass through drain tube 33 nearly at a constant flow. The diameter of the opening through tube 33 is chosen so that there will be some resistance to flow of oil through the tube when the oil is at minimum viscosity. The oil then accumulates above tube 33 until it reaches a level at which the difl'crence in head between the oil level and the top of the tube 33 provides a pressure sufticient to force the oil through the tube at the same rate of flow at which it is discharged from conduit 23.

\Vhen the oil is of higher viscosity, this difference in head does not produce a suflicient pressure. The oil therefore collects in vessel 32 and raises the level until a difference in head is reached, between the oil level and the top of tube 33, which produces a sutticient pressure to discharge oil at the same rate at which it is received in vessel 32. The flow through tube 33 is normally constant, varying only as the oil level changes. The height of vessel 32 is chosen so that the upper edge or mouth thereof will be above the level of the oil when it is at its maximum viscosity, so that there will be no overflow.

It will therefore be seen that the oil level varies with the viscosity, as a higher level is required to force the oil of higher viscosity through the drain tube 33.

As before pointed out, the speed at which the prime mover is governed being within very close limits, the volume discharged from the conduit 23 is practically constant. If the viscosity of the oil discharged from the conduit 23 is at a minimum, the oil level within the vessel 32 may be maintained, for example, as indicated in the drawing. If, however, the oil is at its maximum viscosity, the level thereof within the vessel 32 may be in the upper part of the vessel as indicated by way of example, in the drawing. As the level of the oil within the vessel 32 is raised, its weight therein increases. The vessel 32 is supported by a lever 34 which is fulcrumed at 35 and connected at its opposite end to a link 36 which is, in turn, connected to the valve 28. A spring 37 may be connected to the outer end of the lever 34 for balancing the weight 01': the empty vessel 32 and for providing scale for movements of the lever 34. It will be apparent that upon an increase of weight of fluid within the vessel 32, the valve 28 is moved in an opening direction permitting a greater passage area for the discharge of the pump 19, and thus decreasing the pressure developed by the pump at a given speed.

The operation of the apparatus made in accordance with my invention is as follows: Assume first that the turbine 10 has been standing idle and that the oil within the reservoir 21 is below its normal operating temperature. At the low temperature assumed, the viscosity of the oil within the reservoir is at its maximum and the pressure developed by the pump 19 delivering oil through an orifice of constant area is greater than if delivering oil at a higher temperature. The pump 18 in starting delivers oil at the lower temperature to the vessel 32 and the level of oil within said vessel is raised due to the resistance to flow through the orifice 33, caused by the viscosity of the oil. The increased weight of oil within the vessel 32 pulls the left-hand end of the lever downwardly and opens the valve 28, increasing the passage area through which the pump 19 is discharging to such av degree as to compensate for the viscosity of the fluid assing through the pump 19 and to make the pressure delivered to the governor 13 a true index of the speed of the turbine 10.

As the turbine 10 continues to run, the

- gradually increases in temperature.

temperature of the 011 increases, its viscosity nated.

oil passing through the pumps 18 and 19 As the decreases. and the level of the oil within the vessel 32 is gradually lowered, decreasing the weight of the oil therein. As the weight of the oil within the vessel 82 is decreased, the spring 37 pulls the righthand end of the lever. downwardly, gradually imparting a plosing motion to the valve 28 and' decreasingi the size of .the passage area through which the pump 19 is dischargingt It may thus be seen that whatever the temperature and consequently, the viscosity of the oil within the reservoir .21 and passing through the pumps 18 and 19, the valve 28 assumes a position consonant therewith, and the pressure delivered to the governor 13 is at all times a function of the speed of the turbine 10, 1

From the foregoing, it will be apparent that I have invented an improved fluid pressure governing apparatus employing as a pressure medium a fluid of varying viscosity, wherein pressure differences due to differences in viscosity of the fluid are elimi- While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications, without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is:

1. In a circulating fluid pressure system employing as the pressure medium a fluid of varying viscosity, the combination of two pumps having a common intake and driven in synchronism, separate delivery 7 conduits for the pumps and arranged one to provide relatively large discharge passages wlth a constant head for its associated pump and the other of said conduits arranged with a discharge orifice imposing a back pressure upon the fluid therein, valve means for increasing the discharge area from the last mentioned delivery conduit, and means responsive to the viscosity of fluid discharged from the first mentioned delivery conduit for operating the valve means.

2. In a variablefluid pressure operated governing apparatus for a prime mover employing a fluid of variable viscosity as the pressure -medium, the combination of means for developing fluid pressure vary-" ing as the speed'of the prime mover, and

means for compensating for the viscosity of the fluid comprisin valve means providing a variable flow o fluid from the pressure developing means, means roviding a substantially constant flow of t e pressure medium fluid through a conduit, a vessel weighted by the flow of the fluid thereinto from the conduit and provided with an orifice of constant area for the outflow of fluid therefrom by gravity, and operating means connecting the vessel and the valve means whereby increased weight in the vessel opens said valve means and decreased weight permits said valve means to move in a closing direction. s

3. In a variable fluid pressure operated governing apparatus for a prime moveremploying a fluid of varying viscosity as the pressure medium, the combination of a gear pumpfor developing fluid pressure for operating the governor, valve controlled means for imposing a back pressure on the fluid delivered from the gear pump, a second gear pump driven in synchronism with the first mentioned pump arranged to circulate fluid from a source common to that passing through the first mentioned pump and pumping against a constant head, a vessel having a constant orifice opening below the upper level thereof into which the second gear pump discharges, and an operative connection between the vessel and the valve controlled means for operating said means responsive to the weight of fluid in the vessel.

41 In a fluid pressure operated governing apparatus for a prime mover, said governing apparatus employing as the pressure fluid against a low constant head, a vessel into which the second pump discharges provided with an orifice of constant area adapted to permit fluid in the vessel to flow therefrom by gravity, a lever for supporting the vessel, and an operative connection between the lever and the valve controlled means whereby the' passage area through which the first "mentioned pump discharges is increased by an increase in weight of fluid in the vessel.

with the speed thereof for operating the;

5. In a fluid pressure operated governing apparatus for a prime mover wherein a fluid 0 sure. medium, a fiuid reservoir, a first'and a second pump arranged in parallel within the reservoir, the first of said pumpsdelivering fluid under pressure to the governing apparatus and arranged to discharge fluid back to the reservoir through an orifice for varying viscosity is employed "as the pres-.

imposing a pressure on the fluid for operating the governor, valve controlled means for increasing the orifice area through which said first pump discharges, the second of said pumps delivering fluid through relatively arge passages against a constant head into a vessel having a constant orifice therein below its upper level, a lever su porting the vessel at one end and operative y connected to the valve means at the other end, whereby said valve means is operated responsive to the weight of fluid in the vessel.

6. The combination with a prime mover having a fluid pressure operated governor employing a fluid of varying viscosity as the pressure medium, of two gear pumps driven in parallel by the prime mover and arranged to receive fluid through a common intake, conduit means for conveying fluid discharged from one of said gear pumps to the fluid pressure operated governor, an orifice provided in the conduit for permitting a continuous flow of fluid therethrough and imposing a pressure thereon, valve means for increasing the passage area for the flow of fluid through said conduit, other conduit means providing relatively large passage areas and a constant head for the discharge from the other of said pumps, and means responsive to the viscosity of fluid discharged by the last mentioned pump for varying the position of the valve means.

In testimony whereof, I. have hereunto subscribed my name this twenty-fifth day of September 1925.

HENRY F. SCHMIDT. 

